This invention relates to the mechanical type steam trap and particularly to a float type mechanical steam trap.
The main function of a float type steam trap is to drain condensate from the steam line. The conventional float type steam trap has a single orifice which in turn is operated by a float and lever mechanism. A float valve typically consists of an air tight enclosed ball made of metal or synthetic polymer material connected at the end of a pivoted arm positioned in side a chamber. When a fluid enters the chamber, the ball floats in a fluid such as water and the ball along with its arm tend to move up and down. This up and down movement is used to advantage by connecting an orifice opening and closing element at the end of the arm distal to the ball. This mechanism therefore acts as a valve for controlling the flow of fluid such as water through the orifice. Float type steam traps are so called because they have this type of mechanism installed therein.
Float type steam traps are installed on process vessels to remove condensate. The steam consumption in processes varies with time, which causes variation in the condensate load. At startup, when all processes and steam lines are cold, the rate of condensation is high. In this startup period, the trap has to handle high condensate load. Float type steam traps are sized on the basis of running condensate load and differential pressure across the trap. Hence, the steam trap selected is not able to remove condensate at startup effectively. If steam traps are sized on startup condensate loads and differential pressures across the trap, it makes the steam trap oversized. This results in requirement of more space, extra cost, and bulky installation.
Condensate loads from some processes are high, which may lie beyond the condensate handling capacity of a single orifice float trap. Two steam traps are needed to handle these high condensate loads. This needs more space, cost and the installation is bulkier. In addition, there are several other limitations which exist in the known art.
U.S. Pat. No. 4,276,354 explains a steam trap housing to suit plurality of different inlet and outlet conduit configurations. In this invention condensate handling capacity is limited to the unit selected and it cannot handle variation in condensate loads quickly.
U.S. Pat. No. 4,387,733 reveals a dual fulcrum steam trap having a large initial mechanical advantage and hemispherical valve seat with large contact area, to obtain extended operating life. However since the orifice size is fixed the condensate discharge rate will be limited to the size of the trap selected and will not be able to handle variable condensate loads effectively.
U.S. Pat. No. 4,545,397 reveals a float valve without a lever mechanism, wherein the outer surface of a hollow spherical float operates to open and close an orifice located in the valve seat. The orifice size is related and limited to the size of the float and the trap selected and will not be able to handle variable condensate loads effectively.
U.S. Pat. No. 4,623,091 reveals a float and thermostatic steam trap, in which venting and trapping functions are done by the same valve as the thermostatic actuator acts on the float linkage when the temperature is below a predetermined value. In start-up conditions and when temperature is below the predetermined value the thermostatic actuator engages, forcing the float assembly of the valve to remain open, to vent air and condensate quickly. At temperatures above the preset value the thermostatic actuator disengages completely to allow the float to open and close depending on the level of condensate in the trap chamber. Steam trap as disclosed in this document is able to handle air venting and start-up condensate loads effectively but fails to address the problem of varying condensate loads in conditions above the preset temperature. A steam trap of this design will have to be sized to meet the maximum possible condensate load for any specific application and therefore is likely to be bulky and more expensive.
U.S. Pat. No. 4,706,699 reveals a float operated steam trap in which both sides of the outlet orifice is opened and closed by sensing the pressure prevailing at the inlet of the steam trap. This invention attempts to improve the wear resistance of the valve seats but fails to address the problems of start-up air venting and fluctuating condensate loads that are encountered in normal operations.
U.S. Pat. No. 7,096,880 reveals a float operated steam trap, in this invention a valve closing member slides over a fixed seat to open and close two or more orifices. The float lever carrying the valve closing member uses the force developed by the float to slide the seat across the face of the fixed orifice. The closing member has a surface contact with the valve seat and no positive pressure is applied on the valve closing member to seal it against the valve seat. This will lead to leakage through the orifice, wear and tear due to sliding friction, and the float will have to move over a larger arc with reference to point of pivot specially if the pivot arm is short, to fully open the orifice. As the orifice is not fully open able, condensate flow will be proportionately reduced and larger sized trap will have to be used to handle the required flow rate.
U.S. Pat. No. 7,171,976 reveals a float operated steam trap with collinear inlet and outlet with threaded connection that is easy to install and prevents leakage of live steam. In this invention no provision is made to take care of start-up air venting and fluctuating condensate loads that are encountered in normal operations.
This invention seeks to overcome the limitation of the existing prior arts.